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PubMed2001

Solar forcing of drought frequency in the Maya lowlands.

We analyzed lake-sediment cores from the Yucatan Peninsula, Mexico, to reconstruct the climate history of the region over the past 2600 years. Time series analysis of sediment proxies, which are sensitive to the changing ratio of evaporation to precipitation (oxygen isotopes and gypsum precipitation), reveal a recurrent pattern of drought with a dominant periodicity of 208 years. This cycle is similar to the documented 206-year period in records of cosmogenic nuclide production (carbon-14 and beryllium-10) that is thought to reflect variations in solar activity. We conclude that a significant component of century-scale variability in Yucatan droughts is explained by solar forcing. Furthermore, some of the maxima in the 208-year drought cycle correspond with discontinuities in Maya cultural evolution, suggesting that the Maya were affected by these bicentennial oscillations in precipitation.

Archaeology↗
PubMed2005

Microevolution in prehistoric Andean populations: chronologic mtDNA variation in the desert valleys of northern Chile.

Archeological evidence suggests that the iconographic and technological developments that took place in the highlands around Lake Titicaca in the Central Andean region had an influence on the cultural elaborations of the human groups in the valleys and the Pacific coast of northern Chile. In a previous communication, we were able to show, by means of a distance analysis, that a craniofacial differentiation accompanied the process of cultural evolution in the valleys (Rothhammer and Santoro [2001] Lat. Am. Antiq. 12:59-66). Recently, numerous South Amerindian mtDNA studies were published, and more accurate molecular techniques to study ancient mtDNA are available. In view of these recent developments, we decided 1) to study chronological changes of ancient mtDNA haplogroup frequencies in the nearby Lluta, Azapa, and Camarones Valleys, 2) to identify microevolutionary forces responsible for such changes, and 3) to compare ancient mtDNA haplogroup frequencies with previous data in order to validate craniometrical results and to reconstruct the biological history of the prehistoric valley groups in the context of their interaction with culturally more developed highland populations. From a total of 97 samples from 83 individuals, 68 samples (61 individuals) yielded amplifications for the fragments that harbor classical mtDNA markers. The haplogroup distribution among the total sample was as follows: 26.2%, haplogroup A; 34.4%, haplogroup B; 14.8%, haplogroup C; 3.3%, haplogroup D; and 21.3%, other haplogroups. Haplogroup B tended to increase, and haplogroup A to decrease during a 3,900-year time interval. The sequence data are congruent with the haplogroup analysis. In fact, the sequencing of hypervariable region I of 30 prehistoric individuals revealed 43 polymorphic sites. Sequence alignment and subsequent phylogenetic tree construction showed two major clusters associated with the most common restriction haplogroups. Individuals belonging to haplogroups C and D tended to cluster together with nonclassical lineages.

Base Sequence↗
PubMed2005

The evolution and functions of laughter and humor: a synthetic approach.

A number of recent hypotheses have attempted to explain the ultimate evolutionary origins of laughter and humor. However most of these have lacked breadth in their evolutionary frameworks while neglecting the empirical existence of two distinct types of laughter--Duchenne and non-Duchenne--and the implications of this distinction for the evolution of laughter as a signal. Most of these hypotheses have also been proposed in relative isolation of each other and remain disjointed from the relevant empirical literature. Here we attempt to remedy these shortcomings through a synthesis of previous laughter and humor research followed by (i) a reevaluation of this research in light of theory and data from several relevant disciplines, and (ii) the proposal of a synthetic evolutionary framework that takes into account phylogeny and history as well as proximate mechanisms and adaptive significance. We consider laughter to have been a preadaptation that was gradually elaborated and co-opted through both biological and cultural evolution. We hypothesize that Duchenne laughter became fully ritualized in early hominids between 4 and 2 mya as a medium for playful emotional contagion. This mechanism would have coupled the emotions of small hominid groups and promoted resource-building social play during the fleeting periods of safety and satiation that characterized early bipedal life. We further postulate that a generalized class of nonserious social incongruity would have been a reliable indicator of such safe times and thereby came to be a potent distal elicitor of laughter and playful emotion. This class of stimuli had its origins in primate social play and was the foundation for formal human humor. Within this framework, Duchenne laughter and protohumor were well established in the hominid biobehavioral repertoire when more cognitively sophisticated traits evolved in the hominid line between 2 mya and the present. The prior existence of laughter and humor allowed them to be co-opted for numerous novel functions, and it is from this process that non-Duchenne laughter and the "dark side" of laughter emerged. This perspective organizes the diversified forms and functions that characterize laughter and humor today and clarifies when and how laughter and humor evolved during the course of human evolution.

Adaptation, Physiological↗
PubMed1998

Effect of some physiological factors on nitrogenase activity and nitrogenase mediated hydrogen evolution by mixed microbial culture.

Fermentative H2 evolution, nitrogenase activity (acetylene reduction) and nitrogenase mediated H2 evolution was studied in free cells of mixed microbial population of H2 producers. At 3% glucose level, the cells produced 8.35 l H2/mol glucose utilized. The role of nitrogenase system in H2 generation was evident by derepressed nitrogenase activity (0.46 nmoles C2H4 produced/mg protein/h) under defined in vitro conditions. For maximum expression of the activity, the cells required preactivation under anaerobic conditions by incubating at 40 degrees C for 20-24 h with 0.2% glucose in the culture medium. At an O2 level of more than 0.25%, the acetylene reduction activity decreased significantly and could not be detected at a level of 20%. Nitrogenase activity development was higher at acetylene: inoculum ratio between 4.2-6.25. H2 evolution was lower when the mixed cells were incubated under an atmosphere of 10% C2H2 and 5% CO gas. This decrease in H2 evolution was also evident at 2.5-6.5 mM NaNO3 and KNO3 concentrations in the liquid culture medium thus establishing more than 50% H2 evolution through nitrogenase.

Acetylene↗
PubMed1993

Evolution of a cortical collecting tubule primary culture.

The evolution of a primary culture of rabbit kidney cortical collecting duct (CCT) was followed with the electron microscope using two monoclonal antibodies directed against the principal (Mab 703) and intercalated (Mab 503) cells, respectively. As a result of the loss of the basement membrane surrounding the seeded tubule, the intercalated cells showed a tendency to be eliminated while the basal cytoplasm of the remaining cells consisting mainly of principal cells, quickly spread out at the surface of the filter. Between the first and the seventh hour, cells underwent rapid processes of both dedifferentiation and redifferentiation. At 48 h and later on, they started to proliferate with the production of many multinucleated cells. Normal mitotic divisions, in contrast, were rarely encountered. Whereas the number of intercalated cells as recognized by Mab 503 increased from the fourth day up to the tenth day corresponding to a fully mature culture, culture cells at all time intervals rather resembled principal cells found in the internal part of the cortex or in the outer stripe of the external medulla. It is suggested that in our experimental conditions, dedifferentiated principal cells give rise to both principal and intercalated cells as recognized by immunocytochemistry in the fully developed cell culture.

Animals↗
PubMed2001

Intervening in evolution: ethics and actions.

Biologists should help to guide a process of cultural evolution in which society determines how much effort, if any, is ethically required to preserve options in biological evolution. Evolutionists, conservation biologists, and ecologists should be doing more research to determine actions that would best help to avoid foreclosing evolutionary options.

Bioethics↗
PubMed2005

Behavioural ecology: tool manufacture by naive juvenile crows.

New Caledonian crows (Corvus moneduloides) are the most prolific avian tool-users. Regional variation in the shape of their tools may be the result of cumulative cultural evolution--a phenomenon considered to be a hallmark of human culture. Here we show that hand-raised juvenile New Caledonian crows spontaneously manufacture and use tools, without any contact with adults of their species or any prior demonstration by humans. Our finding is a crucial step towards producing informed models of cultural transmission in this species, and in animals in general.

Animals↗
PubMed2001

The invisible culture of the multiracial, multiethnic individual: a transcultural imperative.

The main purpose of this introductory article is to evoke professional awareness, spark interest, stimulate thought, and disseminate information concerning multiracial, multiethnic (multiple heritage) individuals within the United States. General background information, terms, definitions, ethno-historical influences, practice implications, and current issues will be highlighted. Areas for further exploration will be proposed. Transcultural imperatives urge all nurses and other health care professionals to become active participants in the new cultural evolution of a different, broader worldview that uncovers the "invisible" culture of multiple heritage individuals. The new vision challenges nurse and other health care professionals to embark upon a new journey in the quest for cultural congruent care for all individuals.

Cultural Characteristics↗
PubMed1967

Changing man.

The human condition is changing both culturally and biologically. Although the cultural evolution overshadows the biological, the two are connected by feedback relationships; culture has a biological foundation. Natural selection continues to operate in modern mankind, but its action ought to be supplemented by artificial selection. The problems of the management of human evolution are, however, as much sociological as they are biological. The success of any eugenical program depends on the creation of favorable conditions for human development and self-actualization. In particular, the urgency of the problem of uncontrolled overpopulation exceeds at present that of genetic improvement. Contrary to the alarmist views of some biologists, the evolutionary perspectives for the human species may be regarded as favorable, although, of course, subject to improvement. Man should be the maker of his history, including his evolutionary history. The trend toward increasing social mobility and equality of opportunity may have desirable genetic effects because of the positive assortative mating which it encourages. It makes possible the realization of many hitherto concealed genetically conditioned talents and aptitudes. Rapid progress of both molecular and organismic, Cartesian and Darwinian, biology gives hope of development of new and powerful methods of genetic engineering, control of gene action, betterment of the environment, and improved understanding of the evolutionary processes in the living world, including man.

Biological Evolution↗
PubMed2002

Computational and evolutionary aspects of language.

Language is our legacy. It is the main evolutionary contribution of humans, and perhaps the most interesting trait that has emerged in the past 500 million years. Understanding how darwinian evolution gives rise to human language requires the integration of formal language theory, learning theory and evolutionary dynamics. Formal language theory provides a mathematical description of language and grammar. Learning theory formalizes the task of language acquisition it can be shown that no procedure can learn an unrestricted set of languages. Universal grammar specifies the restricted set of languages learnable by the human brain. Evolutionary dynamics can be formulated to describe the cultural evolution of language and the biological evolution of universal grammar.

Biological Evolution↗
PubMed1991

Evolution and facial action in reflex, social motive, and paralanguage.

Based upon current evolutionary theory and recent laboratory and field data, this paper introduces a behavioral-ecology view of human facial displays that contrasts with previous views of faces as innate, prototypic, "iconic" expressions of fundamental emotions. First, I detail the criteria for establishing genetic and epigenetic contributions to facial behavior. Under these criteria, cross-cultural communality in canonical facial displays implies neither their genetic control nor their fundamental relation to emotion. New findings reestablish phylogenetic continuity by showing that human facial displays and vigilance for them, like their nonhuman counterparts, coevolve in the service of social motives; faces issued in solitude typically reflect imaginary or implicit interaction. Two evolutionary trends are probably involved in shaping facial actions--emancipation of reflexes, and automatization of instrumental acts. Modern conceptions of genetic and cultural evolution, and knowledge about animal signaling, suggest new hypotheses regarding the origins and functions of facial displays. In so doing, they clarify how facial displays relate to reflexion, motive and intention, emotion and psychophysiology, and language and paralanguage.

Animals↗
PubMed2000

Individual development in a bio-cultural perspective.

Biological and cultural inheritance deeply influence daily human behavior. However, individuals actively interact with bio-cultural information. Throughout their lives, they preferentially cultivate a limited subset of activities, values, and personal interests. This process, defined as psychological selection, is strictly related to the quality of subjective experience. Specifically, cross-cultural studies have highlighted the central role played by optimal experience or flow, the most positive and complex daily experience reported by the participants. It is characterized by high involvement, deep concentration, intrinsic motivation, and the perception of high challenges matched by adequate personal skills. The associated activities represent the basic units of psychological selection. Flow can therefore influence the selective transmission of bio-cultural information and the process of bio-cultural evolution.

Adolescent↗
PubMed1995

Culture, gender, and self: a perspective from individualism-collectivism research.

Individualism and collectivism are often equated with independent vs. interdependent, agentic vs. communal, and separate vs. relational self-construals. Although these same concepts have been used to characterize both cultural and gender differences, a perspective of cultural evolution suggests it is unlikely. A division of labor within society may produce gender differences, but this cannot explain cultural differences. A study of self-construal involving 5 cultures (Australia, the United States, Hawaii, Japan, and Korea) shows that differences between these cultures are captured mostly by the extent to which people see themselves as acting as independent agents, whereas gender differences are best summarized by the extent to which people regard themselves as emotionally related to others.

Adolescent↗
PubMed2000

Cremation practices and the survival of ancient DNA: burnt bone analyses via RAPD-mediated PCR.

Numerous burial rites have been developed in different time periods of human cultural evolution. One of the most interesting burial practices was the ritual cremation of human bodies. Due to the respective cultural and religious background, brand graves are known where human remains had been buried together with burnt bones of animal origin. To date, burnt bone samples have been refractory to PCR-mediated amplification. D/L values of aspartic acid far greater than 80 x 10(-3) were measured in the samples thus indicating the presence of severely nicked and fragmented nucleic acids. In order to differentiate between burial gift of animal origin and burnt human specimens we established a highly sensitive protocol that addresses all the shortcomings connected to degraded ancient DNA. With the novel procedure it was possible to classify 4 specimens ranging from 2,000-5,000 BP on the basis of mitochondrial DNA sequences.

Age Determination by Skeleton↗